The present invention relates to a convertible-type motor vehicle. More particularly this invention concerns a folding roof or top for such a motor vehicle.
A standard convertible roof or top comprises a folding framework carrying an outer layer formed of a waterproof, normally plastic, fabric, an inner liner forming the head liner, and an intermediate layer primarily intended for preventing the transmission of sound and heat between the inside and outside. The framework normally includes a plurality of crosswise bows or struts that support the layers and that allow the top to go from a folded down position normally recessed behind the passenger compartment to an up position stretched over the passenger compartment and connected to the upper edge of the windshield.
U.S. Pat. No. 4,964,668 describes such a vehicle top where the outer layer is a skin stretched over the struts which support the inner layer. The outer layer rests virtually directly on the support struts so that there is no insulation at these locations. In addition the outer layer is formed of stitched-together panels which require meticulous treatment to avoid leakage.
German utility model 297 18 206 describes another top where mounting strips secure the support struts directly to the outer layer and the intermediate layer is pinched between the outer layer and the struts. The top structure is fairly complex, requiring many steps to secure the various parts together. In the finished top there is a thermal bridge between the outer layer and the struts formed by the mounting strips.
Further arrangements described in German utility models 69 445 15, 92 06 366, 92 09 122, and 9304 248 are similarly complex. Their assembly is a complex operation and they often leave sites for water or heat to get through the top. The support struts are secured to the outer layer from which the intermediate insulating layer is suspended, or the latter is itself mounted on the struts.
It is therefore an object of the present invention to provide an improved motor-vehicle convertible top.
Another object is the provision of such an improved motor-vehicle convertible top which overcomes the above-given disadvantages, that is which is of simple construction and which provides excellent insulation and water resistance.
A motor-vehicle convertible top has according to the invention a flexible and waterproof outer layer defining a roof having edges and an inner surface, a pair of sides joined at the edges to the roof, and a rear wall extending between the sides and a rear edge of the roof. A heat- and sound-insulating inner layer of a foamable plastic is bonded directly to the inner surface of the roof and inner surfaces of the sides. A pair of reinforcing bands extending along the edges are fixed to the layers. A plurality of crosswise rigid reinforcing struts extend between the bands and secured to the inner layer.
The insulating layer according to the invention is therefore secured directly to the outer layer so that no separate system is needed to retain it in place. In addition the fact that the inner layer runs between the outer layer and the struts means that the thermal- and sound-insulating properties of this inner layer are effective throughout the top, there only being very limited areas where the inner surface of the outer layer is not covered by the insulating inner layer. The molded-in-place foam insulating layer of this invention is extremely effective so that it can be fairly thin and still as effective as the much thicker prior-art systems. Such an arrangement is, of course, equally applicable to other similar uses, for instance in a sun roof.
The outer layer has a textile inner surface to which the inner layer is directly bonded. The inner layer is molded in place in a closed mold under 140 bar to 150 bar pressure, so that it is integrally united with the outer layer. The inner layer is polyurethane and has a Shore D hardness of about 40 and a polyol:isocyanate ratio of about 100:38 by weight. Furthermore the inner layer has a thickness of between 2 mm and 6 mm.
With the system of this invention the outer layer seams are covered and sealed by the inner layer. The closed-cell polyurethane foam used as insulating layer has excellent water-proofing capacities, and bonding it to the inner face of the outer layer effectively seals any potential leak sites. This eliminates any complex extra steps of sealing these seams, for instance by thermally bonding a sealing strip over the inner face at each seam. Furthermore the fact that the inner layer is directly bonded to the outer layer means that this outer layer is stiffened substantially and therefore will not bulge outward during high-speed travel as is common with a skin-type outer layer.
The reinforcing bands are provided with molded-on plastic formations engaged around ends of the struts. In fact these bands can be imbedded along their entire lengths in the inner layer. Since the inner layer lies between the struts and the outer layer, these struts are much less visible from outside, giving the top a smooth shape that is both attractive and aerodynamically efficient. This is particularly true for the strut at the rear end of the roof part where a smooth transition to the back top panel is ensured.
The bands have outer faces turned toward the outer layer and provided with a plastic layer. Furthermore the plastic layer on the bands has interrupted regions so that the bands fold readily at the regions. This plastic layer can be the same as the inner layer and is thinned but not altogether eliminated at the bend zones so that the insulating and sealing effect is not lost altogether.
The inner layer according to the invention is unitarily formed with formations fixed to the struts. These formations are ribs extending along and engaging the struts. Screws or other fasteners can be used to secure the struts in place. Alternately mounting formations such as rubber bands or tapes can be fixed to the struts and imbedded in the inner layer.
The top according to the invention has a roof liner having an inner surface provided with bonded plastic strips in turn having formations fixed to the struts. Thus the roof liner is not attached to the outer or intermediate layer, but to the struts, once again preventing heat or noise from being transmitted through the top in accordance with the invention.